(Not Applicable)
(Not Applicable)
This invention relates to arresting the forward motion of vehicles, such as aircraft overrunning a runway, and more particularly to arresting embodiments with improved resistance to jet blast and other potentially destructive forces.
The problem of aircraft overrunning the ends of runways, with the possibility of passenger injury and aircraft damage, is discussed in U.S. Pat. No. 5,885,025, xe2x80x9cVEHICLE ARRESTING BED SYSTEMSxe2x80x9d (which may be referred to as xe2x80x9cthe ""025 patentxe2x80x9d). That patent, together with U.S. Pat. No. 5,902,068, xe2x80x9cVEHICLE ARRESTING UNIT FABRICATION METHODxe2x80x9d (the ""068 patent) and U.S. Pat. No. 5,789,681, xe2x80x9cARRESTING MATERIAL TEST APPARATUS AND METHODSxe2x80x9d (the ""681 patent) describe arresting beds, units and fabrication methods, and testing based on application of cellular concrete for arresting purposes. The disclosures of the ""025, ""068 and ""681 patents are hereby incorporated herein by reference.
By way of example, FIGS. 1A, 1B and 1C provide top, side and end views of a vehicle arresting bed constructed of cellular concrete blocks for installation at the end of an airport runway. As more fully described in the ""025 patent, an overrunning aircraft enters the bed via a sloped ramp and encounters an array of cellular concrete blocks of increasing height and compressive gradient strength. Such compressive gradient strengths and the bed geometry are predetermined to enable forward travel to be arrested, while minimizing the potential for passenger injury and aircraft damage. In these figures, vertical dimensions and individual block size are expanded for clarity. An actual arresting bed may have dimensions of the order of 150 feet in width, with a maximum height or thickness of 30 inches, and include thousands of blocks of four foot by four foot or four foot by eight foot horizontal dimensions.
Arresting beds constructed pursuant to the above patents, with installations at major airports, have been shown to be effective in safely stopping aircraft under actual emergency overrun conditions. For example, the arresting of an overrunning airliner at JFK International Airport by an arresting bed fabricated by the assignee of the present invention, was reported in the New York Times of May 13, 1999. However, in some applications, depending in part upon particular airport layout, the proximity of jet blast or other physical forces may give rise to deteriorating or destructive effects which could limit the useful life of an arresting bed. Material such as cellular concrete, when used in an arresting bed, must have limited strength to permit compressive failure of the concrete without destruction of the landing gear of an aircraft, for example. Thus, the requirement to limit the strength of compressible material used for arresting purposes, in turn may make the material susceptible to damage or destruction by sonic, pressure, vibrational, lift, projected gravel and other characteristics and effects of jet blast from nearby aircraft, as well as from other sources, such as objects, people or vehicles making contact with an arresting bed other than during actual arresting incidents. As to jet blast phenomena in particular, measured conditions at an end-of-runway arresting bed installation site have included wind velocities to 176 MPH and 150 dB or higher sonic levels.
Accordingly, objects of the present invention are to provide new and improved arresting blocks and beds, and methods relating thereto, which may have one or more of the following characteristics and capabilities:
predetermined performance during aircraft arrestment;
improved resistance to some or all jet blast phenomena;
improved resistance to damage from pedestrian and maintenance vehicle traffic;
improved durability in installations in close proximity to aircraft operations;
improved resistance to atmospheric conditions;
simplified installation and replacement; and
improved resistance to damage during shipment and installation.
In accordance with the invention, a vehicle arresting unit may include a block of compressible material, a top sheet of frangible material, intermediate material between the block and top sheet to reduce transmission of effects of external phenomena (e.g., jet blast phenomena) and a wrapping at least partially enclosing the other elements.
In particular applications, the block may be cellular concrete 6 to 30 inches thick, the top sheet may be cement board about one-quarter inch thick, the intermediate material may be polyethylene foam about one-quarter inch thick and the wrapping may be polyester net. Such a vehicle arresting unit may also include a bottom sheet of cement board and an overlying sealant material having a water resistant characteristic.
Also in accordance with the invention, a method of fabricating a vehicle arresting unit may include the following steps:
(a) providing a block of compressible material having top, bottom and side surfaces;
(b) positioning intermediate material having a force transmission mitigation characteristic above the top surface;
(c) positioning a top sheet of frangible material above the intermediate material; and
(d) securing the top sheet and intermediate material to the block.
In particular applications, step (d) above may comprise at least partially enclosing the block, top sheet and intermediate material in a wrapping, and additional steps of adding a bottom protective sheet and applying sealant material to the unit may be included.
For a better understanding of the invention, together with other and further objects, reference is made to the accompanying drawings and the scope of the invention will be pointed out in the accompanying claims.